net: sched: fix flush on non-existing chain

User was able to perform filter flush on chain 0 even if it didn't have
any filters in it. With the patch that avoided implicit chain 0
creation, this changed. So in case user wants filter flush on chain
which does not exist, just return success. There's no reason for non-0
chains to behave differently than chain 0, so do the same for them.

Reported-by: Ido Schimmel <idosch@mellanox.com>
Fixes: f71e0ca4db18 ("net: sched: Avoid implicit chain 0 creation")
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 0 deletions

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index e8b0bbd0883f..194c2e0b2737 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -1389,6 +1389,13 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
         }
         chain = tcf_chain_get(block, chain_index, false);
         if (!chain) {
+                /* User requested flush on non-existent chain. Nothing to do,
+                 * so just return success.
+                 */
+                if (prio == 0) {
+                        err = 0;
+                        goto errout;
+                }
                 NL_SET_ERR_MSG(extack, "Cannot find specified filter chain");
                 err = -EINVAL;
                 goto errout;